Electron dynamics of active mode-locking terahertz quantum cascade laser* *Project supported by the National Key Research and Development Program of China (Grant No. 2017YFF0106302), the National Natural Science Foundation of China (Grant Nos. 61975225 and 61927813), and Shanghai International Cooperation Project, China (Grant No. 18590780100).

Abstract

The pulse generation from active mode-locking terahertz quantum cascade laser is studied by Maxwell–Bloch equations. It is shown that longer dephasing time will lead to multiple pulses generation from the laser. The dependence of output field on modulation length and radio-frequency parameters is obtained. In order to achieve short pulse generation, the DC bias should close to threshold value and modulation length should be shorter than 0.256 mm. The output pulse is unstable and the envelope shows many oscillations in the presence of spatial hole burning, resulting destabilization of mode-locking.